1. Field of the Invention
This invention relates to a glasses type display apparatus, which displays a picture formed by computer graphics or the like, so that the user experiences a realization (the so-called virtual reality), as if the picture existed in a virtual region in a virtual image. The glasses type display apparatus which is called a head mounted display etc., has right and left display portions displaying left and right pictures respectively, so that the user sees through left and right lens systems a virtual image synthesized with pictures of these left and right display portions.
2. Description of the Related Art
In recent years, a stereoscopic (or three-dimensional effect) television using a lens and a liquid crystal panel or the like has been proposed (see U.S. Pat. No. 4,636,866 (Japanese Patent Laid-Open Gazette No. 117889/1984)). A fundamental principle of such previously-proposed liquid crystal stereoscopic television will be described with reference to FIG. 1.
Referring to FIG. 1, there is shown a convex lens P6 which is composed of a plurality of lenses in actual practice, and a light-transmission-type liquid crystal display P7 is supported in front of the convex lens P6 by a supporting device P8 together with the convex lens P6 to thereby display a video image on a display screen P9 of the liquid crystal display P7. The liquid crystal display P7 is disposed within a focal length F of the convex lens P6. Also, an eye P5 is distant from the convex lens P6 by a distance of 10 to 30 [mm] in the opposite side of the transmission-type liquid crystal display P7.
With the above arrangement, the transmission-type liquid crystal display P7 is disposed within the focal length F of the convex lens P6 so that, when the viewer peeps at a video image on the display screen P9 of the transmission-type liquid crystal display P7 from the eye P5 side through the convex lens P6, the display being illuminated by natural light or guided light P10, the viewer can watch a virtual image P4 in the enlarged form at the position distant from the actual position in which the video image is displayed on the display screen P9.
FIG. 2 is a plan view of the optical system of FIG. 1. As shown in FIG. 2, left and right convex lenses P6L and P6R for magnification are respectively disposed between left and right eyes P5L, P5R and left and right transmission-type liquid crystal displays P7L, P7R, whereby video images displayed on the left and right transmission-type liquid crystal displays P7L, P7R are magnified and also stereoscopic virtual images are displayed on left and right virtual image planes P4L, P4R, respectively.
In the conventional virtual image display device of lens magnification type shown in FIGS. 1 and 2, the left and right convex lenses P6L, P6R are located very close to the left and right eyes P5L, P5R. Thereby, when the viewer wears the virtual image display of this arrangement, the viewer cannot see the view of the surroundings without taking off such virtual image display device, which is very dangerous.
Further, there is a conflict between inclinations (congestion angles) of the left and right eyes P5L, P5R and the focusing adjustment of crystalline lenses thereof. More specifically, video images on the left and right virtual image planes P4L, P4R viewed by the left and right eyes P5L, P5R shown in FIG. 2 must coincide with each other. Whereas, a distance L.sub.1 between the human left and right eyes P5L and P5R is not always the same so that a length L.sub.2 between the left and right convex lenses P6L and P6R must be moved or adjusted. If the length L.sub.2 is changed, the positions of video images displayed on the left and right virtual image planes P4L, P4R will be displaced. FIG. 3 is a schematic diagram used to explain an example such that the video images displayed on the left and right virtual image planes P4L, P4R are displaced in position. In FIG. 3, the virtual image plane P4L is for the left eye and the virtual image plane P4R is for the right eye, and a predetermined point PA.sub.L on the virtual image plane P4L viewed by the left eye P5L and a predetermined point PA.sub.R on the virtual image plane P4R viewed by the right eye P5R should have been displayed at the same position, inherently.
When the viewer watches such an object by this virtual display, inclinations of left and right eyes become .theta.A and .theta.B, which means that the viewer watches a hypothetical point PA on a plane S.sub.1. On the other hand, the left and right eyes P5L, P5R are focused on the points PA.sub.R, PA.sub.L on the virtual image planes P4R, P4L so that the focused states of crystalline lenses and the inclination angles of both eyes are not coincident, thereby viewer's eyes being fatigued.
In the glasses type display apparatus of such a construction, since the user sees through the left and right lens systems, there is a problem of an incongruence of visibility between the lens systems and the user's eyes. For solving the incongruence of visibility, a visibility adjusting means has provided in the glasses type display apparatus.
This adjustment of visibility is ordinarily performed to bring the left and right display portions nearer to or farther from the left and right lens systems. In this case, the left and right display portions are provided on a single moving member to move together. Therefore, when adjusting a visibility, positions of virtual images G.sub.L, G.sub.R are moved as shown in FIG. 4, as a result positions of the virtual images G.sub.L and G.sub.R do not coincide with each other.
In actual practice, even if the positions of the virtual images do not coincide, the user's eyes can view them with correction reaction so that these coincide each other. However, continuing to view with correction reaction for a long time, causes remarkable tension and its attendant ophthalmic fatigue or the like to the user. Thereby, there is a problem that it is caused to the user, such as, an amblyopia and a headache, which becomes a heavy burden to the user.
Generally, the spaces between left and right eyeballs of users, i.e., a distance between pupils, are different normally about 56 to 76 mm. In the glasses type display apparatus, a distance between the left and right lens systems must be adjusted corresponding to various distances between pupils among users. In this manner the display apparatus is more useful when adjusting the distance between lenses, if the adjusted distance between lenses, i.e. distances between pupils, can be easily checked from the outside without using a distance measuring instrument, such as a slide caliper and a ruler etc.
Similarly, if a virtual image display position which is adjusted corresponding to distances between left and right display portions and lenses, can be easily checked from the outside, its usefulness is improved; thus can be realized a convenient glasses type display apparatus in general.
Further, in the glasses type display apparatus used for virtual reality, the so-called goggle type construction as shown in FIG. 5A is ordinarily used. In this case, as shown in FIG. 5B, a space for inserting a pair of glasses within the goggle is provided, considering the user may be wearing glasses for correcting eyesight. However, in this case, when exchanging the glasses, the user must take off the glasses type display apparatus of goggle type construction every time, which is very troublesome.
Further, in the glasses type display apparatus of goggle type construction, because visual fields of the outside of the display portion are obstructed by the case, it is difficult and dangerous, for example, to walk wearing the glasses type display apparatus. Further, the user cannot see other displays while working, thereby if the user wants to see the other displays, the user must take the glasses off at once, thus there arises a problem that work efficiency is lowered.